Nal­cor mum on ques­tions about the North Spur

Let me say up front that I am all for Pre­mier Dwight Ball’s of­t­ex­pressed pol­icy po­si­tion that his gov­ern­ment will “open the books” on Muskrat Falls, and that he will make “ev­i­dence-based” de­ci­sions.

With this in mind, be­low are some facts, some pre­lim­i­nary ev­i­dence, re­lated to the North Spur’s ex­po­sure to, and risk of large, ret­ro­gres­sive land­slides:

• Por­tions of the down­stream, be­low sur­face slope that is in con­tact with the lower quick clay layer has a grade ra­tio (ver­ti­cal to hor­i­zon­tal) ap­proach­ing 1:1.25 (80 per cent) — a grade that is near or higher than Nal­cor’s cho­sen, above wa­ter level, worst case sec­tion B-B “ref­er­ence case.”

• Based on the ex­tent that the large down­stream 1978 land­slide ret­ro­gressed (ate into the nar­row­est part of the North Spur), the sta­bil­ity num­ber for the down­stream side of the North Spur would be 12.

• A sta­bil­ity num­ber of 12 is twice as high as the sta­bil­ity num­ber 6 — the num­ber that en­gi­neer­ing ex­perts Mitchell & Markell say can al­low large, ret­ro­gres­sive (mul­ti­ple fail­ure sur­face) land­slides to oc­cur in East­ern Canada.

• A sta­bil­ity num­ber of 12 is up to four times as high as sta­bil­ity num­ber 3. When the soil’s plas­tic­ity in­dex is be­low 10, a sta­bil­ity num­ber above 3 can al­low large, ret­ro­gres­sive land­slides to oc­cur, and when the plas­tic­ity in­dex is as high as 40 a sta­bil­ity num­ber above 7 to 8 can al­low large, ret­ro­gres­sive land­slides to oc­cur.

• All of Nal­cor’s 123 plas­tic­ity in­dex test re­sults for the lower quick clay layer are be­low 40, and some be­low 10.

• Nal­cor’s 123 liq­uid­ity in­dex test re­sults for the lower quick clay layer have some val­ues cor­re­spond­ing to shear strength val­ues that do not cor­re­late with the nor­mal liq­uid in­dex/shear value re­la­tion­ship. This ap­pears to be a sig­nif­i­cant and yet un­ex­plained anom­aly in Nal­cor’s test re­sults.

• Nal­cor re­ports that some lower shear strength val­ues were de­tected in the south­ern, nar­row­est sec­tion of the North Spur down­stream toe — but that the data/analy­ses was “not re­tained.”

• http://www.vi­sion2041.com/north-spur.html­refers.

My re­quest to Nal­cor for the num­ber, lo­ca­tion and val­ues of its North Spur shear strength test re­sults has gone unan­swered. Mau­rice E. Adams Par­adise

“Nal­cor re­ports that some lower shear strength val­ues were de­tected in the south­ern, nar­row­est sec­tion of the North Spur down­stream toe — but that the data/analy­ses was ‘not re­tained.’”